In a medium skillet, melt 1 tablespoon of the butter. Add the shallot and cook over moderate heat until just beginning to brown, 4 minutes. Add the vermouth and cook until nearly evaporated, about 1 minute. Remove from the heat and stir in the cream cheese, crème fraîche, mayonnaise, mustard, chives and tarragon. Season lightly with salt and cayenne and scrape into a large bowl. Stir in the crabmeat, breaking it up slightly with a spoon. Spread the crab dip in a shallow baking dish or 12 shallow ramekins.

Preheat the broiler. Position a rack 10 inches from the heat. In a small glass bowl, melt the remaining 3 tablespoons of butter in a microwave on high heat. Stir in the bread crumbs and a pinch of salt. Sprinkle the crumbs over the crab dip and broil until the dip is heated through and the topping is golden, about 2 minutes; shift the baking dish for even browning. Serve warm with pita chips or toasted baguette slices.

Make Ahead

The recipe can be prepared through Step 1 and refrigerated overnight. Return to room temperature before broiling.

Suggested Pairing

A ripe but crisp Riesling will highlight the sweet crab and have enough body to complement the cream cheese. Look for an American example. Alternatively, pick a bright, light sparkling wine from Oregon to contrast with the dip's creamy texture.